Issu Overview; Issu Methods - HP 5920 series Fundamentals Configuration Manual

ISSU overview

The In-Service Software Upgrade (ISSU) function enables software upgrade with the least amount of
downtime.
ISSU is implemented on the basis of the following design advantages:
Separation of service features from basic functions. The software of the device includes a boot
•
image, a system image, some feature images, and some patch images (if any). The boot image and
system image provide the operating system. Feature images provide service features. Usually, you
only need to add new service features or upgrade existing service features, without affecting the
basic system functions.
• Independence between service features. When you add or upgrade one service feature, the other
service features and the system operation are not affected.
Support for hotfix. By installing patch images, you can fix system bugs without rebooting the device.
•
Hardware redundancy. A subordinate device in the IRF fabric can take over while the master needs
•
to reboot for an upgrade.
For more information about images, see

ISSU methods

The device provides several ISSU methods. Different ISSU methods apply to different scenarios, require
different upgrade procedures, and have different impact on the running services. The key to a successful
ISSU is to use the recommended method and follow the correct procedure. This section describes the ISSU
methods. For more information about the correct procedures for using these methods, see
ISSU by using issu series
Before an ISSU, use the display version comp-matrix file command to view compatibility between the old
and new software versions and identify the recommended ISSU method. For a compatible version, the
recommended ISSU method is indicated by the Upgrade Way field. For an incompatible version, the
recommended ISSU method "Incompatible upgrade" is displayed after the version dependency
information.
Table 12 shows the ISSU methods for different scenarios.
Table 12 ISSU methods
ISSU method
Incremental
upgrade
ISSU reboot
Reboot
Incompatible upgrade
commands" and
Application scenario
Service-level
Upgrade to a compatible version
File-level
Upgrade to a compatible version
Upgrade to a compatible version
Upgrade to an incompatible version
"Upgrading software."
"Performing an ISSU by using install series
108
"Performing an
commands."
ISSU method indicated by the
display version comp-matrix
file command
Service Upgrade
File Upgrade
ISSU Reboot
Reboot
Incompatible upgrade